In recent years, audio tape decks for use in vehicles have been produced in which tape transport data, e.g. data indicating the tape transport direction, tape transport speed, etc, and also various items of tape playback audio data such as the audio level, etc, are selectively displayed upon a single display region of a display unit. However with prior art methods of controlling such a display arrangement, serious disadvantages arise. Specifically, when the operating status of the tape deck operating mechanism, and hence the tape transport data, is changed (for example as a result of automatic reversal of the tape transport direction) while audio data is being displayed, no indication will be given on the display of such a change in the the tape transport data contents, and the display of tape audio data is continued. Thus, no indication is given to the user that a change in operating status has occurred, or the nature of this change. This is inconvenient for the user, since with such a prior art display control method it is necessary to perform manual actuations of control switches in order to change from a display of audio signal-related data to a display of tape transport data, and it is desirable to minimize as far as possible the amount of manual operations required for a vehicle-mounted tape deck.
In recent types of vehicle audio tape decks, a spectrum analyzer function is also included whereby frequency analysis of the playback audio signal is performed and the results are displayed in spectrum analyzer form, i.e. as a bar graph display produced on a display panel having a rectangular array of display segments, such as a fluorescent segment display panel. The frequency parameter is measured along the horizontal axis of the display, and signal level is measured along the vertical axis. Such a frequency analyzer display occupies a large part of the control panel of a vehicle tape deck, so that it is difficult to accommodate an additional display region for indicating the operational status data, i.e. for displaying the direction and speed of tape movement, etc. It would therefore be desirable to employ a method of display control for such a tape deck whereby the operating status data could be displayed by the same segment array that is used to display the spectrum analyzer data. Such a control method should also permit various other items of audio playback signal data, such as the audio signal level, to be displayed in place of the spectrum analyzer display when desired.
In addition, such recent types of vehicle audio tape decks also may include a graphic equalizer function, whereby a desired graphic equalizer characteristic can be set by the user, and subsequently memorized, through actuation of switches while observing a graphic equalizer display produced on the aforementioned segment display panel. In order to minimize the amount of operations which must be performed by the user, it would be desirable to provide a method of display control for such a tape deck whereby actuation by the user of any of the switches used in graphic equalizer operation would cause the display of graphic equalizer data to be immediately initiated, and whereby after a predetermined time interval has elapsed following such a graphic equalizer operation switch actuation or any other graphic equalizer operational activity, the data which was being displayed immediately prior to the initiation of the graphic equalizer display would be immediately restored.